Method of using a parallax scanning lens aperture in a range-finding application

ABSTRACT

A lens aperture of an autostereoscopic camera is moved in a parallax scanning pattern through a plurality of disparity positions offset from the optical axis of the camera lens. Images of a scene being photographed, as viewed through the lens aperture in its various disparity positions, are recorded for subsequent display in three dimensional illusion when viewed with the unaided eye. The size of the lens aperture and the parallax scanning pattern are adjustable to suit conditions. The lens aperture may be defined as a through-hole in an opaque card or a planar array of cells switched between transparent and opaque states. In addition to stereoscopic imaging, the moving lens aperture principle of the present invention may be utilized in range-finding and camera image stabilization applications.

REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 08/456,408, filed Jun. 1,1995, now U. S. Pat. No. 5,699,112, which, in turn, is a division ofSer. No. 08/148,916, filed Nov. 5, 1993, now U.S. Pat. No. 5,448,332.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to a stereoscopic apparatus and method forproducing images that can be displayed as three-dimensional illusionsand more particularly to an autostereoscopic imaging apparatus andmethod for producing images that, on display, can be perceived to bethree-dimensional without the use of special viewing aids.

II. Prior Art

The production of two-dimensional images that can be displayed toprovide a three-dimensional illusion has been a long standing goal inthe visual arts field. Methods and apparatuses for producing suchthree-dimensional illusions have to some extent paralleled the increasedunderstanding of the physiology of human depth perception.

Binocular (stereo) vision requires two eyes to view a scene withoverlapping visual fields. Each eye views a scene from a slightlydifferent parallax angle and focuses the scene unto a retina. Thetwo-dimensional retinal images are transmitted by optic nerves to thebrain's visual cortex, where they are combined, in a process known asstereopsis, to form a three-dimensional model of the scene.

Depth perception of three-dimensional space depends on various kinds ofinformation (cues) perceived from the scene being viewed, such asrelative size, linear perspective, interposition, light and shadow,gradients (monocular cues), as well as retinal image size, retinaldisparity, accommodation, convergence (binocular cues), and familiaritywith the subject matter of the viewed scene (learned cues).

Retinal disparity, which is the separation between a person's eyes,provides parallax information. It is now well known that depthperception can be achieved when left and right eye depth information ispresented alternately to the brain, as long as the time interval doesnot exceed 100 milliseconds. It has been demonstrated that the brain canextract parallax information from a three-dimensional scene even whenthe eyes are alternately covered and uncovered for periods up to 100milliseconds each. The brain can also accept and process parallaxinformation presented to both eyes if sequenced properly. The ideal viewcycle sequencing rate has been determined to be between 3-6 Hz.

True three-dimensional image displays can be divided into two maincategories, stereoscopic or binocular and autostereoscopic. Stereoscopictechniques (including stereoscopes, polarization, anaglyphic, Pulfrich,and shuttering technologies) require the viewer to use a viewing device,such as polarized glasses. Autostereoscopic techniques, such asholography, lenticular screens, parallax barriers, alternating-pairs andparallax scans produce images in a true three-dimensional illusionwithout the use of special viewing glasses.

Prior art autostereoscopic television and motion picture systems haveutilized the approach of alternately displaying views of a scenerecorded by two cameras from different points of view. U.S. Pat. No.4,006,291 to Imsand; U.S. Pat. Nos. 4,303,316 to McElveen; U.S. Pat. No.4,429,328 to Jones et al.; U.S. Pat. No. 4,966,436 to Mayhew & Prichard,all utilized two cameras to record horizontally, vertically, or acombination of horizontally and vertically displaced views of a scene.While this autostereoscopic approach produces images which providethree-dimensional illusion when displayed, precision matching of the twocameras is required. Improper alignment of the cameras, lens mismatchesin focal length and/or focus, chrominance and illuminance mismatches,and misplaced convergent points all contribute to image instability.Also, considerable operator skill is required to continuously adjustdisparity, convergence and time-displacement rates of image recordingsin a coordinated manner to maintain a stable image.

Image stability can be rendered less noticeable by the use of maskingtechniques. Camera motion is very effective in hiding rocking motions ofimages, apparently because the brain places less importance on rockingmotion than on camera motion. This could result from some sort ofnatural stabilizing phenomena or mechanism of the brain that allows usto see clearly while walking or running, when images would otherwisebounce.

To avoid the drawbacks associated with a two-camera autostereoscopicsystem, autostereoscopic methods and apparatuses using a singlecamera/single lens have been developed. Mayhew et al. U.S. Pat. Nos.5,014,126 and 5,157,484 disclose single camera autostereoscopic systemscapable of recording images which, when displayed, are perceived by aviewer in three-dimension. Commonly assigned, copending U.S. patentapplication No. 08/115,101, filed Sep. 2, 1993 by Fernekes et al.discloses a method and apparatus, wherein a single camera records imageswhile undergoing oscillatory parallax scanning motion.

While the single camera autostereoscopic imaging systems disclosed inthe above cited prior art are effective in producing high quality,stable images that can be perceived in three-dimension when viewed withthe unaided eye, unfortunately the apparatuses are rather bulky andheavy, relatively complex in construction, and consume a meaningfulamount of power in operation.

SUMMARY OF THE INVENTION

A principle objective of the present invention is to provide improvedmethod and apparatus for producing images in two-dimension that, upondisplay, can be perceived as three-dimensional with the unaided eye. Themethod and apparatus of the invention utilize an autostereoscopicapproach to three-dimensional imaging, thus avoiding the drawbacksinherent in the stereoscopic approach. The autostereoscopic method andapparatus of the present invention utilizes a single imaging device,such as a motion picture or video camera, and thus the disadvantages ofa two-camera autostereoscopic approach are avoided. Moreover, theapparatus of the present invention is compact in size and light weight,efficient in construction and operation, and convenient to implement inconventional motion picture and video cameras.

To achieve these objectives and advantages, the improved single-cameraautostereoscopic imaging method of the present invention comprises thesteps of providing an imaging lens having an optical axis directedtoward a scene, providing a lens aperture, moving the aperture relativeto the lens in a parallax scanning pattern through diverse disparitypoints displaced from the optical axis of the lens, generating asuccession of time-spaced images of the scene as viewed through theaperture from a plurality of the disparity points, and recording theimages. This method can be practiced using an imaging device, such as amotion picture camera or a video camera, or a computer suitablyprogrammed to simulate the lens, the aperture and the lens aperturemotion.

The apparatus of the present invention, in its most basic form, includesan imaging plane, a lens for focusing images of objects in a field ofview on the imaging plane, an optical element positioned adjacent thelens and providing an aperture, and an actuator for oscillating theoptical element such as to produce a parallax scanning motion of theaperture relative to the optical axis of the lens. A succession oftime-spaced recordings are made of the object images focused on theimaging plane, as viewed through the aperture from a plurality ofdifferent parallax views or disparity points offset from the lensoptical axis.

By virtue of the method and apparatus of the present invention, displayof the two-dimensional image recordings in corresponding time-spacedsuccession can be perceived as a three-dimensional illusion.

The single camera autostereoscopic imaging method and apparatus of thepresent invention are readily conducive to numerous modifications. Theaperture may be located in front of or behind the lens or between lensesof a multiple lens set. The aperture may take a variety of sizes andshapes, be adjustable in size and/or have different edgecharacteristics. Furthermore, more than one aperture may be utilized.The pattern of the parallax scanning motion of the aperture may be of avariety of configurations ranging from circular to rectangular tocomplex lissajous configurations. The optical element may take the formof one or more opaque cards having one or more through-holes or slitsserving to create a lens aperture. Also, the optical element can beimplemented as a liquid crystal panel or a ferro-electric panel (spatiallight modulator) providing a matrix array of cells that can beselectively switched between opaque and transparent states.

Moreover, depth information derived from the images of objects viewedthrough the lens aperture during parallax scanning motion can beutilized in range finding applications. In addition, controlled lensaperture movement can be utilized to compensate for spurious cameramotion and thus stabilize image recordings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and are intended toprovide further explanation of the invention as claimed.

The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitutepart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partially in schematic form, illustratingone embodiment of the present invention.

FIG. 2 is a perspective view, partially in schematic form, illustratingan alternative embodiment of the invention.

FIG. 3 is a perspective view of an alternative form of optical elementthat can be utilized in the embodiments of FIGS. 1 and 2.

FIG. 4 is a side view, partially in schematic form, of anotherembodiment of the invention.

FIGS. 5(a)-5(d) illustrate various aperture configurations that may beutilized in the embodiments of FIGS. 1 and 2.

FIGS. 6(a)-6(f) illustrate alternative parallax scanning patterns thatmay be executed by the optical elements in FIGS. 1-4.

FIG. 7 is a schematic diagram illustrating various controls that wouldtypically be applied to the autostereoscopic imaging embodiments ofFIGS. 1 and 2 in practicing the present invention.

FIG. 8 is a front view of an alternative optical element usable in theembodiments of FIGS. 1, 2 and 4.

FIG. 9 is a flow chart illustrating an application of the presentinvention to computer generated imaging.

FIGS. 10(a)-10(c) are schematic diagrams illustrating the operation ofthe autostereoscopic imaging apparatus of the present invention.

FIG. 11 is a schematic diagram illustrating the application of thepresent to range finding.

FIG. 12 is a schematic diagram illustrating the application of thepresent invention to camera image stabilization.

FIG. 13 is a schematic diagram illustrating the application of automaticdisparity control to the autostereoscopic imaging apparatus of thepresent invention.

Like reference numerals refer to corresponding parts throughout theseveral view of the drawings.

DETAILED DESCRIPTION

The autostereoscopic imaging apparatus of the present inventiondisclosed in FIGS. 1-8 is directed to a stereoscopic imaging applicationwherein a succession of time-spaced images of a scene are recorded by asingle imaging device in a manner such that a subsequent display of theimages can be perceived as three-dimensional. Thus, as seen in FIG. 1,an autostereoscopic imaging apparatus, generally indicated at 20,includes an imaging plane 22 of a suitable imaging device such as a filmcamera or video camera. Reference 24 indicates a camera lens which inpractice typically comprises a set or system of multiple lenses. Lens 24has an optical axis 25 which is directed at a distant object 26 in ascene to be imaged. In a conventional manner, the position of lens 24 isadjusted forwardly or rearwardly, as indicated by arrow 27, along itsoptical axis to focus an image 26a of object 26 on imaging plane 22which represents the film plane of a film camera or a CCD array of avideo camera.

In accordance with a signal feature of this embodiment of the presentinvention, an optical element 28, consisting of an opaque card 29 inwhich is formed a through-hole or aperture 30, is positioned betweenobject 26 and imaging plane 22. FIG. 1 illustrates an optical elementposition immediately behind lens 24, i.e., between the lens and imagingplane 22, while FIG. 2 illustrates optical element 28 immediately infront of lens 24. Preferably, the optical element is located as close aspossible to the lens iris (not shown) which can be positioned betweenlenses of a multiple lens set typically used in a camera. Ideally,optical element 28 would assume the position of and replace the lensiris.

The optical element is mechanically linked, as schematically indicatedat 32, to an actuator or motor 34 which operates to move aperture 30 ina parallax scanning motion relative to lens optical axis 25. A circularparallax scanning pattern for aperture 30 is illustrated by arrow 36 inFIG. 1, while a rectangular scanning pattern is illustrated by arrow 38in FIG. 2. Other parallax scanning patterns are illustrated in FIGS.6(a)-6(f). Normally the aperture scanning patterns are centered aboutlens optical axis 25, however, under certain conditions, desirablevisual effects can be achieved when the scanning pattern is off-centeredrelative to this optical axis. While scanning patterns will typically belimited to horizontal (X) and vertical (Y) coordinate motions in theplane of optical element 28 and transverse to optical axis 25, it willbe understood that Z coordinate motion parallel to the optical axis, asillustrated by arrow 35 in FIG. 1, may be introduced in conjunction withX and Y coordinate motions for special effects and to mask motionartifacts.

With reference to FIG. 2, it is seen that light rays 40 from the top ofobject 26 pass through aperture 30 and are redirected by lens 24 towarda lower location on imaging plane 22 where a focused image of the objecttop is formed. Similarly, light rays 41 from the bottom of object 26pass through aperture 30 and are redirected by the lens toward an upperlocation on the imaging plane where a focused image of the object bottomis formed. Light rays from objects portions between its top and bottomlikewise pass through aperture 30 and lens 24 to complete the formationof focused image 26a. If an image 26a is recorded while aperture 30 isin the position shown in FIG. 2, it is seen that the point of view ofthis image has a vertical disparity represented by arrow 42 which isequal to the distance below optical axis 25. If the object image isrecorded while the aperture is in phantom line position 30a indicated inFIG. 2, the point of view has a disparity equal to the vertical offsetabove the optical access as represented by arrow 42a. Similarly, imagerecordings taken while aperture 30 is in phantom line positions 30(b)and 30(c) have horizontal disparities equal to the aperture horizontaloffsets from the optical axis 25.

Disparity, whether horizontal or vertical or components of both, islargely responsible for adding parallax to visual images. Portions ofobject volumes having essentially flat surfaces produce images whichappear flat and two-dimensional. Changes in the viewing perspective donot change the appearance of these portions. However, portions of aobject volume naturally having depth when viewed directly, do changetheir appearance or, more specifically, their position and aspect, asthe viewing perspective is changed. Changes in the viewing perspectivecreate corresponding edges on the image which do not perfectly matchwhen the images are superimposed. Alternatively displaying these imagescreates contrast at these edges which is perceptible to the brain asdepth.

FIG. 3 illustrates an alternative embodiment of an optical element,generally indicated at 50, for use in the apparatus of FIGS. 1 and 2.This optical element includes a pair of opaque cards 52 and 54 arrangedin juxtaposed, parallel relation. Card 52 is provided with a verticallyelongated, rectangular slit 53, while card 54 is provided with ahorizontally elongated, rectangular slit 55. At the intersection ofslits 53 and 55, a rectangular lens aperture 56 is created. An actuator58 reciprocates card 52 in the horizontal direction, as indicated byarrow 58a, and an actuator 60 reciprocates card 54 in the verticaldirection, as indicated by arrow 60a. It is seen that, by virtue of therelative motions of the cards, scanning motion of aperture 56 isproduced. By adjusting amplitude, frequency, and phase of the cardreciprocating motions, the lissajous parallax scanning patternsillustrated in FIGS. 1, 2 and 6(a)-6(f), as well as many other patterns,are readily achieved. While the lens aperture configuration is circularin FIGS. 1 and 2 and rectangular in FIG. 3, it may take other shapes,such as, for example, elliptical as illustrated in FIG. 5(a), octagonalas illustrated in FIG. 5(b), and cruciform as illustrated in FIG. 59(c).FIG. 5(d) illustrates that the lens aperture may have a soft or frayededge, rather than a hard or sharp edge.

Regardless of the lens aperture configuration, it is important that itbe bordered throughout by the opaque material of the optical element 28.Also, the parallax scanning pattern of the lens aperture should remainwithin the effective aperture of lens 24, which typically corresponds to80% of the lens diameter. Thus, the size of lens aperture 30 should besignificantly less than the size of this effective aperture of the lens,so that the lens aperture can assume disparity positions of sufficientlydifferent reviewing perspectives (disparity) needed to provide depthperception. It will thus be appreciated that, as the size of lensaperture 30 increases, the depth of field, disparity, and exposure timewill all decrease. Conversely, smaller lens aperture sizes providelarger depths of field, accommodate greater disparities, and requirelonger exposure times.

While the embodiments of FIGS. 1-3 utilize a single parallax scanningaperture, plural apertures may be utilized. As seen in FIG. 4, a pair ofoptical elements 70 and 72 are respectfully formed with lens apertures71 and 73. Optical element 70 is positioned behind lens 24, and opticalelement 72 is positioned in front of the lens. Optical element 70 isoscillated by an actuator 74, while optical element 72 is oscillated byan actuator 76. These actuators are controlled by a controller 78 toproduce parallax scanning motions of apertures 71 and 73. The scanningpatterns of the two lens apertures may be of the same or differentconfigurations and may be in synchronism with or independent of eachother. The use of two parallax scanning apertures may be used forspecial effects and/or to mask a motion artifacts of object 26 as imagedon imaging plane 24.

FIG. 7 illustrates lens 24, optical element 28 and actuator 34 carriedby a lens mount, schematically illustrated in phantom line at 80. Alsoincluded on the lens mount is an F stop adjustor 84 for adjusting thesize of lens aperture 30 in accordance with available light and desireddepth of field. Lens mount is moved fore and aft (arrow 85) by focusadjustor 86. A controller 88 may be provided to control actuator 34 to adesired parallax scanning motion for lens aperture 30, control F stopadjustor 84 to a desired lens aperture size, and control focus adjustor86 to bring into focus a desired subject in the field of view.

As illustrated in FIG. 8, an optical element can also be implemented asa liquid crystal or ferro-electric panel (spatial light modulator),generally indicated at 90. These panels include a matrix array of cells92 which can be individually addressed and activated by a driver 94 tocreate one or more transparent cells 92a amongst a remainder of opaquecells 92b. The transparent cell or cells 92a thus constitute a lensaperture 96 which can be readily moved about in a variety of parallaxscanning patterns, including those illustrated in FIGS. 6(a)-6(f), bydriver 94.

It will be appreciated that driver 94 may be externally, manually orautomatically controlled, as indicated at 98, to vary the size and shapeof aperture 96, as well as the configuration of the parallax scanningpatter of the aperture. Moreover, as indicated at 96c, driver 94 canreadily introduce one or more parallax scanning or stationary lensapertures, in addition to aperture 96, to create special effects or tomask motion artifacts. Also, rather than abruptly switching the cellsbetween transparent and opaque states, the transition may be effectedsomewhat gradually through progressively changing degrees of gray scale.In practice, driver 94 and controller 98 may be implemented by asuitably programmed digital computer.

The principles of the present invention may also be applied in thecomputer generation of images which then can be displayed inthree-dimensional illusion. FIG. 9 illustrates the basis steps involved.In step 100, an object and object motion are defined inthree-dimensional space, and a scene to include the object is alsodefined in three-dimensional space in step 102. The imaging device orcamera, camera positions (points of view), illumination, range, etc.,are defined in step 104. Camera definitions include simulations of animaging plane, lens and lens aperture parameters, such as size andshape. In step 106 the image is rendered by simulating a desiredparallax scanning pattern of the lens aperture using a suitable raytracing algorithm, and the rendered images are stored in computer memoryon a frame-by-frame basis (step 108). The stored images can then beretrieved from memory for display on a computer monitor, recorded onvideo tape for display on a TV screen and/or recorded on film forprojection on a screen (step 110).

From the foregoing description, it will be noted that, since only thelens aperture undergoes parallax scanning motion while the lens 24remains stationary, the point of view of the lens aperture is alwaysconvergent on the object to which the lens is focused.

Thus, unlike prior single-camera autostereoscopic imaging apparatuses,such as disclosed in, for example, the cited U.S. patent applicationSer. No. 08/115,101, a separate convergence adjustment is avoided in theapparatus of the present invention. That is, focus adjustment inherentlyestablishes the appropriate convergence setting, which is an importantfeature of the present invention.

FIGS. 10(a)-10(c) are schematic diagrams illustrating how this importantfeature of the invention can be used to an advantage. In FIGS. 10(a),10(b) and 10(c), objects A, B, and C represent objects at close range,mid-range, and far range, respectively, relative to imaging plane 22. Iflens 24 is focused on far range object C, as depicted in FIG. 10(a), theimage of this object appearing on imaging plane 22 remains stationaryduring parallax scanning motion of aperture 30. However, when aperture30 moves upwardly to positions of vertical disparity above optical axis25, for example, the images of objects A and B appearing on imagingplane 22 move downwardly, as indicated by phantom lines 120, relative tothe stationary image of object C. Conversely, when aperture 30 movesdownwardly to positions of vertical disparity below the optical axis,the images of objects A and B appearing on the imaging plane moveupwardly, as indicated by phantom lines 122, relative to the stationaryimage of object C.

When lens 24 is focused on object B, as illustrated in FIG. 10(b), theimage of this object remains stationary as aperture 30 undergoesparallax scanning motion. As the aperture scans upwardly, throughpositions of vertical disparity above optical axis 25, the image ofobject A appearing on imaging plane 22 moves downwardly, as indicated inphantom line at 123, relative to the stationary image of object B, whilethe image of object C appearing on the imaging plane moves upwardly, asindicated in phantom line at 124, relative to the object B stationaryimage. When the aperture moves downwardly through positions of verticaldisparity below optical axis 25, the reverse conditions obtained, i.e.,the image of object A moves upwardly (phantom lines 125), and the imagefrom object C moves downwardly (phantom lines 126) relative to thestationary image of object B.

If lens 24 is focused on close range object A, the images of objects Band C move upwardly, as indicated by phantom lines 127, relative to thestationary image of object A, when aperture 30 scans through verticalparallax positions above optical axis 25. Conversely, the images ofobjects B and C move downwardly, as indicated in phantom line at 128,relative to the stationary image of object A when the lens aperturemoves through vertical disparity positions below the optical axis.

This phenomena of relative motions of images of objects in the lensfield of view observed during parallax scanning motion of lens aperture30 can be utilized to advantage in range finding applications.Considering FIG. 10(c), assume that aperture 30 is scanned betweenpositions of maximum vertical disparity (maximum offset from opticalaxis 25) to maximize the image motion of object B relative to thestationary image of object A to which the lens 24 is focused. If thedistance between object A and a camera reference point, such as imagingplane 22, is known, the distance between object A and object B can bedetermined from the magnitude of the motion of the object B imagerelative to the object A image or from the peak-to-peak amplitude,indicated at 129, of the object B image motion. Such determination canbe accurately computer calculated by triangulation using recorded imagesof objects A and B taken, for example, from extreme disparity pointsabove and below optical axis 25. Alternatively, the measured amplitude129 of object B image motion produced by aperture parallax scanningmotion between extreme vertical disparity points can be used to access alook-up table and thereby determine the separation between objects A andB. It will be appreciated that a rather close approximation of the rangeof objects A, B and C from imaging plane 22 can be obtained by adjustingthe focus of lens 24 to any one of these objects until the image of thisobject becomes stationary as appearing on imaging plane 22. The objectrange can then be determined from the focus setting that completelyquiets all motion of the object image as observed on a video screendisplaying the object image.

FIG. 11 illustrates an application of the present invention to arange-finding video camera 130 mounted by a robotic arm, generallyindicated at 132. The video camera, located on the robotic arm in areference position, is oriented to view a scene including a stationaryreference object 134 and a target object 136 which is to be griped by ahand 133 of the robotic arm. The distance between video camera 130 inits reference position and reference object 134 is known. When thecamera lens is focused on reference object 134, images of the referenceand target objects are recorded as the lens aperture undergoes parallaxscanning motion. The recorded images are analyzed by a computer 138 todetermine the range of the target object relative to the camera based onthe magnitude of target image motion relative to the stationaryreference image and the known distance between the camera and thereference object. Knowing the target object range, the computer canreadily control the motion of robotic arm 132 to bring hand 133 rapidlyinto the grasping relation with target object 136. It will beappreciated that video camera 130 may be stationed at any fixedreference position a known distance from reference object 134, ratherthan being mounted by the robotic arm.

By virtue of the present invention, parallax information sufficient todetermine target range can be acquired using a single imaging device,e.g., video camera. This is a distinct advantage over the conventionalpractice of using two video cameras or sets of parallax mirrors andprisms.

Another application of the present invention is illustrated in FIG. 12,which utilizes a moving lens aperture 30 to compensate for spuriousmotion of an imaging device 140, such as a film or video camera, andthus to stabilize the images of an object 26 focused on the imagingplane 22 of the camera. To implement this application of the invention,camera 140 is equipped with an inertial sensor 142, such as anaccelerometer. This sensor sends signals indicative of camera motion toa controller 144 which translates the camera motion signals into drivesignals for actuator 34 drivingly connected to optical element 28. If,during imaging of object 26, camera 140 experiences spurious upwardmotion, sensor 142, via controller 144, signals actuator 34 to moveoptical element 28 and thus lens aperture 30 downward. Downward cameramotion induces upward motion of the lens aperture. It will beappreciated that by moving lens aperture in the opposite direction tospurious camera motion, the images of object 26 focused on the cameraimagining plane by lens 24 can be stabilized against such camera motion.Image stabilization by compensating motion of the lens aperture inaccordance with the present invention can be implemented quiteinexpensively as compared with the current practices ofgyro-stabilization of the entire camera or the use of moving mirrorsand/or prisms to compensate for camera motion and thus steady the objectimages appearing on the camera imaging plane.

The motion of objects in a scene being imaged, such as objects A, B andC in FIGS. 10(a)-10(c), can also be used to automatically control lensaperture motion. Thus as illustrated in FIG. 13, a camera 150, such as avideo or film camera, is aimed to view a scene 152 including objects A,B and C. The camera lens 24 is adjusted to focus the image of one ofthese objects on an imaging plane 22. Images of the scene are stored ona frame-by-frame basis in an image frame buffer 154. A computer 156compares successive stored image frames, such as by subtracting one fromthe other, to quantify the motion characteristics of the images of theother objects relative to the stationary image of the focused object.The quantified motion characteristics are used by a controller 158 toadjustably control the parallax scanning motion, produced by actuator34, of lens aperture 30 in optical element 28. In this manner, a desiredthree-dimensional effect can be automatically achieved by constantlymonitoring the motions of object images appearing on imaging plane 22and adjusting amplitude (offset of disparity positions from lens opticalaxis) and frequency of the lens aperture scanning motion according tothe extents of relative image motions.

While the present invention has been described in the context of movinga lens aperture in a parallax scanning motion, as images of objects arerecorded, at a rate of three to six Hz, it will be appreciated thateffective depth perception of displayed images or object range can beachieved by providing an optical element which can alternatingly createa lens aperture at different disparity positions offset from the lensoptical axis. Thus, rather than moving a single aperture in a parallaxscanning motion through different disparity positions, an equivalentparallax scanning motion can be achieved by utilizing an optical elementor combination of optical elements operated to create momentary lensapertures at various disparity positions vertically, horizontally and/orboth horizontally and vertically offset from the lens optical axis.Using this approach, the optical element or elements can function as thecamera shutter, as well as the lens aperture. The optical element ofFIG. 8 is particular suited for this approach to the practice of thepresent invention.

It will be apparent to one skilled in the art that various modificationsand variations can be made in the autostereoscopic imaging apparatus ofthe present invention without departing from the scope or spirit of theinvention. Thus, it is intended that the present invention covermodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

I claim:
 1. A method of autostereoscopic imaging comprising the stepsof:providing an imaging plane; providing a lens having an optical axis;directing the optical axis toward an object; creating a lens aperture ata succession of disparity positions offset from the optical axis;observing an image of the object appearing on the imaging plane; andadjusting the lens to a focus setting that eliminates motion of theobject image appearing on the imaging plane.
 2. The method of claim 1,further including the step of determining object range from the focussetting.